Signaling system



March 3, 1942.`

J. T. MCNANEY 2,275,017

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L o 'j N u U u l s D In Patented Mar. 3,` 1942 UNITED STATES PATENTOFFICE y SIGNALING SYSTEM Joseph T. McNaney, Baltimore, Md.

Application June 18, 1940, Serial No. 341,196

My invention relates to signaling systems and it has a particularrelation 4to high speed systems of the type wherein a perforated tape orthe like is utilized at the transmitter and means at the receiver areutilized for making a permanent record of a received message.

Heretofore, in systems of the general type to which my inventionpertains, the limitation upon the speed of transmission and receptionhas been largely mechanical. That is to say, referring for example toteletype systems, the inertia of the moving parts at thel receiver 1prei/ents ultra high speed and in printing telegraphs the sameAlimitation appears.

It. is, accordingly, an object ofvmy invention to provide a signalingsystem wherein the speed of `transmission and reception is substantiallyunlimited, within reason, and a permanent record of the message isformed.

Another object of my invention is to provide trical impulsesrepresentingmessage-characters may be translated into light and thelight therefrom is of such nature that it may be utilized for thepurpose of making a photographic record.

A still further and, more 4specific object of my invention is to providea novel receiving tube of the cathode ray type that shall' be capable oftranslating incoming electrical impulses representing characters of amessage into visible replicas of the said characters, which replicas maybe utilized for photographic recording.

The novel features lof my invention are set .forth with particularity inthe appended claims;

the invention itself, however, both as toits organization and its methodof operation, togethcr with additional objects and advantages thereof,will best be understood from the following description of a specificembodiment when read in connection with the accompanying drawings,wherein:

.Figure 1 is a diagramamtic view, highly conventionalized, of asignaling system embodying my invention,

Figure 2-is a view of a perforated tape of the type utilized in thetransmitting portion of vmy system,

Figure 3 is a view partly in section exemplifying the manner in whichthe perforated tape is utilized for the purpose of providing a pluralityof groups of electrical impulses, each group of impulses beingrepresentative of a'message-character, i

Figure 4 is a circuit diagram exemplifying the utilization ofphoto-electric currents for the purpose of controlling the modulation ofa transmitter.

Figure 5 is a circuit diagram of `a receiver utilized in my system,

Figure 6 is a conventionalized view, partly in section, of my novelcathode ray translating tube andexemplifying the manner inwhich the tubeis employed for the purpose of photographically recording an incomingmessage,

Figure '7 is a view in vertical section of a gunelementof the cathoderay tube shown in Figure 6,

Figure 8 is an enlarged View of one of the diaphragms in the elementshown in Figure '7,

Figure 9 is a view in vertical elevation of the electron gun Vasesmblyexemplified by Figure 6, looking into the tube from the recording endthereof,

f Figure 10 is a fragmentary view, partly in section and partly invertical elevation, exemplifying an alternative form of my cathode raytube.

Figure 11 is an enlarged sectionalized view of one of the electron gunsshown in Figure 10,

Figure 12 is a fragmentary view in vertical section exemplifying analternative embodiment of my invention, and

Figure 13 is an enlarged elevational view of a portion of the apparatusshown in Figure 12.

In accordance with my invention, I provide means for transmitting twomodulated carrier waves by wire or radio, the said waves being utilizedat the receiving end of the system for determining the momentary anglesof deflection of a locally generated cathode ray, the coordinates of theposition of the ray in turn determining a particular character-of atransmitted message. More specically, referring now to Figure 1 of thedrawings, at the transmitting end of the system, I provide two radiotransmitters I and 3, two carrier frequency generators 5 and 1, twosignal frequency generators 9 and H, and two modulators I3 and l5, thepercentage of modulation in each modulator being determined,simultaneously, by the output from two photo electric cells I l and I9.At `the receiving end, it being understood that the two transmitterssend ony different carrier frequencies, I provide two 93, in series withan y'frequency depends receivers 2l and 23 permanently tuned to thecarrier frequencies and two converters 25 and 21 for changing theincoming signals to D. C. potentials, which potentials aresimultaneously' impressed across pairs of deflecting plates 29 and 3l ina cathode ray receiving tube.

For the purpose of providing message modulated light for the twotransmitting photo-electric cells, i1 and I9 I provide, as shown inFigures 2 and 3,`a perforated tape 33 that is caused to advance betweenthe photo electric cells and a pair of light sources 35 and 31, thelight falling on the photo tubes being limited by two slots. 39

and 4I in a mask 43 interposed between the said tubes and the lightsources.

Referring still to Figure 2, it will be noted that the tape carries aplurality of paired groups of perforations disposed at each side of thecenter thereof, the groups extending transversely of 'the tape inalignment with the respective slots in the ',mask, whereby, when thetape is caused to advance between the light sources and the photo tubesthe amount of light reaching each tube is determined by the number ofperforations momentarily interposed between it and its individ-` uallight source. It will also be noticed that thev several transverse slotsinthe mask are narrower than any perforation through the tape,considered in the direction ofthe travel thereof, whereby each groupofmvthe said perforations dwells for a short space`of time before theslot corresponding toit. The slots in the actual ap-v paratus are muchnarrower than shown in the drawings.

In Figure 2, I have made no attempt to exemplify an actual message buthave shown instead the manner in-which the transverse paired groups ofperforations may be so designed as to the relative number ofperforations per group that 49 separate and distinct characters may betransmitted. It may be pre-punched by any suitable device.

The manner in which each one `of the two photo electric cells isutilized in the transmitter to modulate a carrier wave is' exemplifiedby the transmitter diagram of Figure 4. The spaceycurrent path in aphoto tube is connected in series in. In the operation of the apparatus,when no light through the perforated tape reaches the photo electriccell, the resistor 5| across which the signal frequency is impressed isso adjusted that the normal self-bias applied to the grid from thecathode resistor 51 is just suiiicient to permit 100% modulation of thecarrier frequency in the modulator tube. Obviously, when light fallsupon the cathode of the photo electric cell, the bias applied to thetube becomes more negative, thus lessening the percentage of modulation.The amount of modulation of the carrier of each transmitter frommaximum, or 100%, toward zero is controlled in seven discreet stepsdepending upon the number of perforations in the group'of perforationsthat momentarily permitsv light to reach the corresponding photo cell.

Referring once more to Figure 2 of the drawings, it will be noted thatthe paired groups of perforations allocated, respectively, to each ofthe forty-nine characters are so chosen that the each photo-cellreceives the same amount of light, this amount being the greatest of thesevendifferent amounts controlled by the perforations, and thepercentage of modulation of each carrier will be changed from 100% tothe lowest of the seven predetermined amounts. Again, if the character Gis being transmitted, it will be t noted that one unit of light reachesone of the with a source 45 of potential and a biasing resistor 41,which resistor-.is included in the input circuit of a thermionic tube 49in series with an additional adjustable resistor across which amodulating frequency at constant' amplitude is impressed. The modulatingfrequency, for example,v may be within the audible range, such l as onethousand cycles or the like, and it is preferably the same for bothphoto tubes. The anode circuit of the thermionic tube includes theprimary coil 53 of a transformer, a source 55 of potential and aself-bias resistor 51 shunted by a by-pass condenser 59.

The secondary coil 6| of the transformer is included vin the anodecircuit ofA a modulator tube impedance device such as a tuned circuit65. The carrier frequency is impressed upon the input circuit ofthemodulatortube 63 from an' oscillator (not shown) and appears across theimpedence device, modulated by the signal frequency which is introducedinto the anode circuit winding of the transformer.

'I'he percentage of 'modulation of the carrier upon vthe amplitude ofthe signal frequency supplied to the anode circuit from thephoto-cell-controlled tube 49; the said signal frequency amplitude, inturn, is a function f of the negative bias applied to the grid of thethereof from the secondary photo-tubes while seven units of light reachthe other tube. In that event, one carrier is modulated at the highestpercentage of the seven predetermined amounts eblow while the othercarrier is modulated at the lowest of the seven predeterminedpercentages.

Each character is represented by analogous dissimilar paired groups ofperforations. This feature of my invention is very important because,`as will be clear to those familiar with mathematics, each character maybe denoted by X-Y coordinates. As an example, referring also to Figure9, A could be represented by -7X, rIY; G by -X, 7Y; T by -2X, 5Y, andlso on with the remaining characters, each character thus being capableof being represented by a definite locus in a plane. The manner in whichI take further advantage of the geometric relation betweenthe'perforation-groups and of the consequent Igeometric relation of thepercentages of modulation of the two carrier waves,

in the receiver, will be apparent hereinafter.

Referring now to Figures `1 and 5 of the drawings, two modulated carrierwaves are received by l two separate radio receivers 2| and 23 tuned,respectively, thereto and two D. C. potentials are derived therefrom bytwo converters 25, 21. The

amplitudes of the D. C. potentials are proport As shown in Figure of thedrawings. the receiver and converters are conventional in designcomprising a detector 61 and ampiler and a thermionic tube Il having anauxiliary diode circuit on which the detected and amplified signal isimpressed. The last mentioned tube functions in a manner well known tothose skilled in the art and provides, across a resistor 13 included inthe output circuit thereof, a D. C. potential proportional to theamplitude of modulation of the incoming carrier wave.y VInasmuch as eachreceiver is` provided with AVC, the 100% modu- Such a tube has at oneend thereof a thermionic cathode "l5, a grid 1l, an electron gun 19 andtwo pairs of deecting plates 29 and 3l. At the `extreme opposite end ofthe tube the interior surface carries a layer- 8! of lluorescentmaterial such as Willemite or. the like. At the position intermediatethe two ends of the tube is disposedV a transparent screen 83 coated, onthe side facing the deflecting plates, with a layer 85 of flu'- orescentmaterial. Opposite the side of the screen facing the fluorescent end ofthe composite tube, which screen may be curved as shown in the drawings,is mounted a metallic supporting element 81- provided with forty-nineconical cups 89 having their larger openings exposed to the partitionbearing the fluorescent material and their smaller openings pointingtoward the open ends of an equivalent number of electron guns 9| carriedand electrically connected together by a second metallic supportingelement. The cups and lthe electron guns corresponding thereto arearranged, substantially as shown in Figure 9, in seven rows, each rowcomprising seven cup-gun combinations. The cups and guns, therefor, havedefinite X--Y coordinates as explained in connection with thedescription of my transmitting tape.

Preferably, the composite tube takes substantially the form of a doublecone with the fluorescent screen interposed at the junction of the basesthereof and the electron guns mounted in f that portion, the end ofwhich carries the fluorescent screen. Each of the'guns, which may bemade from nickel or an analogous material, is

provided as shown in Figure 7 with one or more Aelectron-limitingperforated diaphragms 95, 9T,

` uorescent screen, emits photo electrons and the 'cups l89 aremaintained at a negative potential with respect to the guns 9|. Thepotential may be derived from any suitable source such as a battery IUI,the most positive point in the source being connected to a focusinganode 103 mounted within the tube. The portion of the tube, extendingtoward the deflecting plates, is also supplied with an interior`focusing anode |05 which is maintained at a high positive potentialwith respect to the thermionic cathode l.

In the operation of the receiving tube, potentials determined by thelight received by the several transmitting photo-cells, as the tapemoves before them, are impressed from the two-receiver converters,Vrespectively, across the several pairs of deflecting plates. When thesetwo potentials are equal and maximum, corresponding to the no-signalcondition, the cathode ray assumes a position designated n in Fig. 9. Ifnow the letter A" is transmitted and received, the modulation of eachcarrier is reduced seven units, and-the ray is deflected to a positionon the main fluorescent screen in front of the cup-gun combinationwherein the diaphragm 91 has an opening conforming in contour to thatletter. Such position might be represented by the notation -7X, TYAnalogous dissimilar pairs of 'potentials, each less than the maximumcorresponding to '100% modulation at the transmitter, causeproportionall deections of the cathode ray which ray dwells on theproper spot on the screen'for the space of time required for a row ofperforations to travel between the photo-cells and the light sources inthe transmitter.

Light emitted by the main iiuorescent screen 85, at any given positionof the deected ray, falls upon the interior surface of the conical cup89 allocated to that position andcauses the emission of photo-electronsthat are accelerated through the corresponding gun 9| to ultimatelyimpinge upon the small iluorescent screen 8l at the recording end of thetube. As the stream of electrons emerges from the gun, it.has a crosssection corresponding to the contour of the character-perforation in theinterior gun-diaphragm.

, For example, ifthe gun-diaphragm is provided the moving lightsensitive material.

with a U-shaped perforation, as shown in Figure 8, onlythose electronscorresponding to the U will pass therethrough and will be shot againstthe iluorescent screen 8| at the extreme end of the tube and thereatwill be reeonverted into a visible image of the said character for thepurpose of recording the said character.

A lens system IGT is provided which focuses light from the fluorescentscreen onto a moving strip 109" of photo-sensitive material. A diaphragmIII having an opening H3 therethrough may be interposed between the lenssystem and Obviously, the 'entire apparatus may be enclosed in alighttight housing to prevent the light-sensitive material fromreceiving any light other than that transmitted to it from thefluorescent screen by way of the lens system. The speciiic arrangementofthe housing and other details of the lm advancing mechanism form no partof my present invention and, for that reason, they have not beenillustrated.

The lm or other light-sensitive material is given continuous motion pastthe opening in the mask, the rate of travel being commensurate with therate of travel of the perforated tape of the transmitter. By this, Imean that the linear speed of the record-receiving material should `hesuch that an unexposed portion thereof is moved into place during theinstant of time consumed by the cathode ray in moving from one point onthe uorescent screen to another.

Because of the fact that the cathode ray itself is devoid of inertia thespeed of transmission is limited only by the rate at which thetransmitting tape may be caused to mov past the transmitting photocells, fthe photo-sensitivity of the record receiving material and theVmaximum speed at which the said` material may be caused to pass throughthe apparatus. problems has led me to the conclusion that the ultimatespeed obtainable by my improved system is much greater than with anyother system heretofore utilized, although at this time I am unable tostate with certainty the maximum number of words per minute the systemis capable of handling.

Instead of converting the cathode ray into light and reconverting thelight into an electron stream to represent a character of a message, itlies within the scope ofv my invention to utilize the deflected cathoderay itself, reinforced by secondary electrons, for that purpose.Referring to Figures and 11, when employing the cathode ray direct thecentral ,fluorescent screen 83-85 is omitted and the cups 89 areprovided with an inner coating of material that freely emits secondaryelectrons when under-bombardment by the ray. A suitable coating isaluminum oxide.

In order to more eiiiciently make use of the cathode ray, the cups arefocused, so to speak,

upon the'opening of the gun 'I9 in -the cathoderay generating portion ofthe composite tube; the construction of the small guns trained on thefluorescent screen is the same as that shown in Figures 6 and '7.

When receiving a signal by` means ofthe alternative embodiment ofmyinvention, the cathode ray, as it dwells withinthe opening of particularcup 89 corresponding toa message-character being momentarily received,causes the l emission of secondary electrons. Such secondary electrons,together with electrons from the rayitself, are accelerated through thesmall gun 9| associated with the cup because of the positivev potentialapplied thereto. The contour of the electron stream is determined by theperforation in the diaphragm 91 near theend of the small gun and themodified stream, under the influence of the potential of the focusinganode, strikes the fluorescent screen in the end of the 'tube to providea visible image of the character.

It also lies within 'the scope of my invention to omit the perforateddiaphragm in the small guns and to control the cross-section of eachminor stream of electrons directly at its source.

` That modification is exemplified by Figs."l2 and 13 of the drawingsand comprises the partition 83 carrying the main iiuorescent screen 85as exemplified by Figure 6. I dispense, however, with the cups carryingphoto-emissive material and, instead, deposit such material on thesurface of the partition, facing the small electron guns, in the form ofa character H5 itself. The characters electrically interconnected inorder that they My research into these common axis thereof by connectingthem to successively more positive points on a voltage source |`l9 thenegative terminal of which is connected sients, such as static, willaffect both receivers to may be maintained at a negative potential withrespect to the associated electron guns. For that purpose, the surfaceof the partition may be provided with a substantially transparentmetallic coating of gold or silver by the well known sputtering processbefore the characters are formed thereon. The coating is too thin toillustrate.

Because of the fact that the electron .stream at its origin; has theproper cross 4section to represent-amessage character, the small guns 9|may each be a' plain cylinder devoid of diaphragms or they may beconstituted by a plurality of rings H1, as shown in Figure 12, Whenrings are used,

substantially the same degree and, consequently they will give rise toequal decrements of potential across the pairs of deflecting plates.Even if strong, static will only urge the cathode ray diagonallyof thescreen toward the zero position thereon corresponding to% modulation.If, as a result of static, therefore, a character is omitted from therecorded message it may easily be interpolated by reference to a chartsuch as shown in Figure 9. The appearance of any recorded characteritself cannot be marred by interference, because the ray must dwell foran appreciable length of time on a given portion of the screen to giverise to a photographic representation of the character.

No synchronization of the transmitter and the receiver is necessary asin other well known systems becausethe transmitter tape does not have torun at the same speed asthe lm.

The receiver being free of moving parts and electrical contacts is lesslikely to .give trouble, at the same time being more reliable.

The high speeds possible will permit greater use of expensive land linesand submarine cables.

A signaling system of this type has possibilities for` secret signaling.

Although I have shown. and described a few specific embodiments of myinvention, many other modifications thereof will be Yapparent to thoseskilled in the art to which it pertains. My invention, therefore, is notto be limited except bythe prior art and by the spirit of the appendedclaims. v

I claim as my invention:

1. In a signaling system, means for generating and for transmitting twocarrier Waves, meansfor simultaneously and individually modulating saidwaves to predetermined percentages in accordance with amessage-character, two receiving devices for individually receiving saidmodulated waves, means connected to each receiving device for derivingtwo unidirectional potentials proportional,v respectively,rto thepercentages of modulation of the received Waves, a cathode ray tubeprovided with two independent ray-deflecting systems at one end, afluorescent screen at the. opposite end, means interposed between theray-deecting systemsandl the screen for deriving a plurality of minorelectron streams from the cathode ray, and means for simultaneouslyimpressing said unidirectional potentials upon 4 .ing said modulatedwaves, means connected to each receiving device for providing anunidirectional potential proportional to the percentage of a potentialgradient is maintained -along the steps.

3. The invention set forth in claim l, whereinr the modulating meanscause the two carrier waves to -be modulated in denite, predetermined 4.The method of signal transmission .which comprises generating twocarrier waves having diierent constant frequencies, causing each wave tobe modulated at a substantially constant lower frequency, causing thepercentage of modulation of each wave to diierentially vary inpredetermined steps, the relative percentage of modulation of the twowaves corresponding to a definite message-character, and causing saidwaves to simultaneously travel to a remotely disposed receiver.

5; The method of signaling which comprises generating and transmittingtwo modulated carrier waves simultaneously, causing the percentage ofmodulation of said waves to differentially change in accordance with amessage character, deriving two unidirectional potentials from saidwaves proportional, respectively, to the percentages of modulationthereof` at any given instant, generating a cathode ray, utilizing saidpotentials to control the angular deflection of said ray, and

making a record of the coordinates correspondgenerating and transmittingtwo modulated carj rier waves simultaneously, causing the percentage ofmodulation of said waves to diierentially change in accordance with amessage-character, deriving two unidirectional potentials from saidwaves proportional, respectively, to the percentages of modulationthereof at any given instant, generating a cathode ray, utilizing saidpotentials to control the angular deflection of said ray, deriving astream of secondary electrons from the ray, utilizing the secondaryelectrons to energize a fluorescent screen and making a photographicrecord of the instantaneous appearance of said screen.

7. The method of signaling fwhich comprises generating and transmittingtwo modulated carrier waves simultaneously, causing the percentage ofmodulating of said waves to diierentially change in accordance with amessage-character, derivingtwo unidirectional potentials from said wavesproportional, respectively, to the percentages of modulation thereof atany given instant, generatinga cathode ray, utilizing said potentials tocontrol the angular deflection of said ray', causing the ray to controlthe generation 0f a stream of secondary electrons proportional insection to the angular deflection of the cathode 4 ray, and deriving aphoto-chemical effect proportional to the cross-section of the secondaryelec-

